The overall goal of this application is to understand the mechanisms by which highly specific modulation of ion channel function is achieved. The first project focuses on the KCNQ family of K+-selective ion channels expressed in neurons, heart and epithelia. The proposed studies will analyze the mechanisms of ion channel modulation by a slow signaling mechanism activated by M1 muscarinic receptors. Structure-function studies will be carried out on cloned KCNQ channels expressed in a cell line to elucidate molecular determinants of their modulation. Other ion channels that respond to the unknown messenger underlying slow modulation will be identified. Candidate messengers and candidate target regions on channels will be characterized to try to identify the messenger. The second project is to study the specificity of G-protein signaling system. The proposed studies will identify the modulatory intermediates and targets of neurotransmitter action on Ca2+ channels of the pituitary-derived GH3 cell line and characterize the specificity and molecular determinants of modulation of Ca2+ channels in neurons by G-protein beta and gamma subunits. These studies should reveal biochemical mechanisms of several key intracellular signals in neurons and provide a better understanding of the biomedical processes in which modulation of channel activity are involved, which include control of heart rate, secretion from endocrine and exocrine glands, and psychiatric changes of state.